Electric discharge lamp and controlling means therefor



March 4, 1947. w. J. HARRIS 2,416,751

ELECTRIC DIS CHARGE LAMP AND CONTROLLING MEANS THEREFOR Filed Jan.2,1945

If 'm m 'P m Patented Mar. 4, 1947 OFFICE ELECTRIC DISCHARGE LAlVIP ANDCON- TROLLING MEANS THEREFOR William James Harris, Newport, EnglandApplication January 2, 1945, Serial No. 571,047 In Great Britain January5, 1944 1 Claim. 1

This invention relates to electric discharge lamps, fluorescent orotherwise, and controlling means therefor, of the type in which the lampconsists of an envelope containing gas such as mercury or sodium vapourr neon, with or without a proportion of argon, into the ends of whichenvelope are sealed two filamentary electrodes (these latter preferablyhaving associated alkaline earth oxides) and in which the controllingmeans includes an automatically operating or other starting switch whichwhen closed and upon the mains voltage being applied to the lamp, allowscurrent to pass to the electrodes sufiicient to raise them toincandescence and to start ionisation of the gas in their immediatevicinity, and when opened effects the breaking of the circuit throughthe electrodes to permit other means remaining in the circuit to give ahigh voltage kick or surge through the gas between the electrodessuificient to start the discharge through the lamp, and has for itsobject so to devise the controlling means that such lamps can be startedand run with efficiency on direct current, even of comparatively lowvoltage.

In general, in accordance with the invention, the lamp proper is made inany usual manner and the controlling means for the lamp comprises anelectromagnetic inductance co-operating with a make-and-break device.This latter forms the starting switch of the control and is connected inthe circuit in the position for such switch and comprises a movablearmature or its equivalent at least partly of magnetic material, whilstthe inductance is such and so mounted in the circuit that it forms themeans for inducing the necessary high voltage when, with the lampconnected to the mains, the starting switch is opened. In addition, theinductance and armature are so juxtaposed that when the lamp isconnected to the mains the magnetic flux of the inductance is adapted toattract the armature against resilient return means to effect theopening of the starting switch, the said flux being suiiicient at alltimes, even after starting, to maintain the said switch open. Further,the windings of the inductance'also act as a limiting device for thecurrent consumed by the lamp.

Preferably, the main switch between the mains and the lamp circuit is ofa one-direction rotary type so that the polarity of the electrodes isreversed upon successive lightings of the lamp, to eliminate defects dueto electrophoresis.

In most cases and for convenience, the control is included in thestructure of the lamp, for example in a. compartment at the back of atrough- 2 like or other hood or shade of the lamp, although it may beseparate from the lamp.

It will be understood that when the lamp is not connected to the mains,the make-and-break device is held by the resilient return means so thatit is closed, in other words the starting switch is closed, and thearmature comes at the maximum distance from the adjacent end of theinductance. As a consequence, when the mains switch is next operated,current at mains voltage passes through the two filamentary electrodes,the inductance and the make-and-break device. The electrodes come toincandescence and start the ionisation oi the gas in their immediatevicinity. Also, the magnetic flux commences to attract the armature andthis latter is moved thereby to break the contact of the startingswitch. This causes the voltage surge and if the partial ionisation ofthe gas has been adequate, then this voltage surge is sufiicient tostart the discharge of the lamp. The current continues to flow throughthe inductance and its magnetic flux keeps the armature of the startingswitch in the open position.

Should, however, the preliminary heating by the electrodes beinsufiicient, then upon the openin of the starting switch and after theconsequent voltage surge no current will continue to flow through theinductance, and as a consequence the armature, not beingmagneticallyattracted, will again be brought by the resilient return means tocontact-making position. Thus, a trembling action may take place for ashort period until the starting ionisation of the gas in theneighborhood of the electrodes is sufilcient for the induced highvoltage consequent upon an opening of the starting switch, to start thedischarge through the lamp.

Upon moving the main switch to switch off the lamp, the magnetic fluxthrough the inductance ceases and the armature returns to thecontact-making position, in other words the starting switch is closedready for the next operation of the main switch, and so on. If this mainswitch is of the one-directional rotary type, then on the next operationthe polarity of the electrodes will have been reversed.

In order that the invention may be better understood, it will now bedescribed with refer- ,ence to the accompanying drawings which are givenby way of example only and in which Fig, 1 is a somewhat diagrammaticcross sectional elevation of one form of electric discharge lamp andcontroltherefor constructed according to the invention, assembled as aunitary structure with a trough-like reflector and shade.

Fig. 2 is a plan of Fig. 1 with parts in section.

Fig. 3 is a diagram of a lamp and control in accordance with theinvention when the lamp is not connected to the mains and with thestarting switch in the closed position. I

Fig. 4 isa similar view to Fig. 3 but'showing the lamp connected to themains and with the I starting switch in the open position.

The inductance to be employed in any case, that is to say the number ofturns and the gauge of the insulated wire used, depends 'upon thevoltage of the supply and the wattage of the lamp. In a particular casefor a-fluor'e'scenttu- Joular lamp of standard dimensions, '60" long:and 1 diameter, rated at 80 watts toloperate at substantially 230volts, the inductance comprises six coils. Each coil is a multi-layercoil with a hollow core of desired diameter and is made up from 3283turns of 27 gauge insulated copper wire,

the outside dimensionsofthe coil being'substantia'lly 6" long and 1diameter.- The complete "inductance is constituted by connecting the sixcoils in series and'arranging them end to end in :axial alignment.

" 'In 1 the drawings; is the electric discharge lampof--standingdimensions with two-pin *bayonet end-capstoengage theequivalent sockets wot a trough'refiecton and shade 5 in anyusuala--man-ner. Theshade at its rear has a compart- --ment1 whioh'h'ouses aninductance formed'by ksixcoils 8 connected in series and arranged end toend in axial alignment as hereinbefore described. It also houses acasing 9-in which the =rnake-and-break or starting switch is-located- IThe starting switch may take man forms. 'As

-.diagrammatically shownin Fig. 2, it comprises an armature formed froma stem H! and head I I "of magnetic material, the stem entering andbe-si' ing adapted to slide in the hollow core of the first call 8 oftheinductance.

The head II is kept pressed outwards by a spring I2. On the side of thehead remote from the spring, this head has a contact I3 which in theclosed position of then? -starting switch ,is in electricalconnectionwith another contact l4 carried by a fixed conducting supportIS the position of which preferably is adjustable, by a screw {6. Thespring l2 keeps'the contacts l3 and M in electrical connection'whenithelamp is not lit. Any suitable connections are 3 provided so that" thecontacts'l3 and M are included in the oircuitof' the starting switch.

As shown in Figs. Sand 4, thestartingswitch is comprised by a pivotedarmature ll having a con-n tact I8 and a head l9 ofmagnetic material."The contact l8' co-operate's'with'another contact 2c barri'edby afixedsupport 2! the position of which preferably is adjustable'bya'screw22.The coning switch and remain in this position while the lamp is alight.

Except fertile-leaders to the main switches;

all "the leads' between the parts preferably are housed in thela'mpstructure and are indicated by (exterior dotted lines imFig; 1 and morefully parf ticularised in the diagrams Figs. 3 and 4.- From 'tHGS latteril'vWill be" s li'thakfi one lead 24 iS'CO nected to one end of afilamentary electrode 26 the other end of this electrode being connectedto the fixed contact 20 of the starting switch. The armature IT is aconductor or has an associated 5 conductor and this is connected to oneend of the other electrode 21 the other end of this lastmentionedelectrode being connected to one end 1 of the inductance, the other endof the inductance being connected to the other lead 24. Thefirstmentioned lead 24 is connected to a contact 28 "of the main switch25 which is a one-direction rotary starting switch and the other lead 24to the next contact 29 of the said switch. 3% and 3| are two furthercontacts of the starting switch to which themains 32 for D. C. currentof de- Y sired voltage (230 volts in the particular case underconsideration) are connected. The starting switch is symmetricallyarranged and the movable conducting parts of the switch are such thatthe polarity of the contacts 28 and 29 thereof is reversed .onsuccessivea..operations .loi the switchto bringthe lamp into the .D. .C.circuit; f-Fig- 3' shows a switched-ofhpositionsL By movement'in thedirection of the arrow. 33, theswitch is brought' into theposltionlshown inFig. 4 to switch the lamp intocircuith 'By.furthermovement of 45 inthe same .directionfrom the position'shownin'Flg. 4, thelamp is again switched 'offgand so on. As each successiveswitching-on reverses .the polarity of .thecontacts iii and 29 o'f-theswitch, thepolarity of .the electrodes 25 and ZI also is reversed. 1

Inoperation it will be understood with. the partsin the position shownin Fig. 3, that imme- -diately the current isswitched on by. the switcha 25. a circuitis completed from..the. contact .28 of the switch 25throughthe. filament 23,.through the make-and break contacts zii. and.i8, through the armature l1, through the other filament .21, cthroughthe: inductanceucomprised by the .six coils 8 .in series, back touthecontact .29 ofthe switch. Thisicircuitiremains. completed. for an-extremelyshortperiod, during whichhowever. the filaments 26r-and'21 arebrought toincandescence to start ionisation of the gas in theirimmediate vicinity. After this hasbeen efiectechthe mag- 1 netic fiuxiof the inductance attracts. the) armature H' t'oseparate the contacts.l8 and. 20*(or I3 w 14, Fig. 2). Thisiinduces a: very highs-voltso ageby thecollapse of the magnetic fieldoi; the 1 inductance coilsandenables the currenti to overcome theresistance of the gases'inthe-lamp to start the-discharge between therelectrodes' :25 I and 21,which latter of course are nolonger incandescent.

I The parts are now in-sthe position shown in "Fig. l-and now that thegas path is a conductor (represented-by the dotted arrows" 3 i, Fig. 4),although -the connections from the filaments to the make-and breakswitch are no :longer in cir- --'cuit, the vsaidgas pathcomes inseries-withthe inductance; coils -8 so that the-magnetism due to thecurrent-passing through :thesaid coils keeps the armature ll attracted,maintaining the conta'cts l8 and 2ilapart Moreover, .the; coils tisalsoactas a limiting 'device forthe current consumed by the lamp. I 1

is When the switch '25 is operated to switch the la'mp'from the circuit,then. the currentthrough thegas path is broken to-cause the cessation ofthe illumination andno current. passes-through the coils 8, which.enables the.spring;23 to return the armature' H: to the contact-makingiposition readyfor'thelampxagainto be switched: on. I Electric 'rdischarge: lamps, tparticularlyi o1 isthe fluorescent type, and controlstherefor, in accordance with the invention, in practice have been foundhighly efiicient both from the aspect of consumption and illumination.After lighting, they run without flicker and no part of the lamp or thecontrol has a temperature greater than slightly above room temperature.One such lamp of the standard type hereinbefore mentioned operating at230 volts on D. C. with the control according to the invention, alreadyhas had a total illuminated life of over 5,000 hours, its electricalefllciency being unimpaired whilst its luminous efliciency has fallenofi but slightly.

The exact arrangement of the inductance for any particular case willdepend upon the voltage and wattage, and further upon the housingcapacity for the coils. Generally, the lower the voltage the fewer thetotal windings of the inductance and/or the thicker the gauge of thewire used. It is preferred to make up the inductance in separate coilssuch as 8 in the drawings of desired numbers of turns and of a desiredgauge wire and to utilise as many of such coils as is desired in anyparticular case.

In connection with the make-and-break device with its armature, whateverthe exact construction, in some cases a damping device may be utilisedof the diaphragm or other type and operating by air or other fluid. Thisacts to delay the opening of the starting switch for a short period, forexample a few seconds and then allows a quick break to give thenecessary voltage surge.

The system according to the invention enables fluorescent or otherelectric discharge lamps to be satisfactorily operated either fromdirect current mains, or batteries, or accumulators, in fact from any D.C. supply and at any convenient voltage. As a consequence of thesatisfactory operation of such lamps from D. C. sources, it is possibleto utilise these fluorescent or other electric discharge lamps not onlyin fixed positions such as in streets and buildings, but also invehicles such for example as trains, trams, omnibuses, motor roadvehicles generally, aircraft, shipping and otherwise.

The invention is not limited to the precise forms or details ofconstruction herein described, as

6 these may be varied to suit particular requirements.

What I claim and desire to secure by Letters Patent of the United Statesof America is:

A starting and operating circuit for gaseous electric discharge lampshaving two filamentary electrodes sealed into the envelope of the lamp,including an automatically operating starting switch which when closedand upon the supply voltage being applied to the lamp allows current topass through the electrodes sufiicient to raise them to incandescenceand to start ionisation of the gas in their immediate vicinity and whenopened eifects the breaking of the circuit through the electrodes topermit an -electro-magnetic means remaining in the circuit to give ahigh voltage kick through the gas between the electrodes sufficient tostart the discharge through the lamp, said starting switch being formedby a make-and-break device held closed when the lamp is unlit andincluding a movable armature, said electro-magnetic means being formedof an electro-rnagnetic inductance comprising a coil greater in lengththan in diameter and having a hollow core arranged with its axisparallel to the axis of the envelope of the lamp, the armature of thestarting switch extending movably into said hollow core of theelectro-magnetic inductance, the parts being so relatively positionedand constructed that the armature is subject to the magnetic fluxproduced by the energized inductance to cause the armature to beattracted'and drawn farther into the coil to open the starting switch,and spring means for returning the armature to a position in which thelatter closes the starting switch upon de-energization of saidinductance.

WILLIAM JAMES HARRIS.

REFERENCES CITED UNITED STATES PATENTS Name Date Babb Apr. 25, 1939Number

